See attached screenshots, one from Emacs 23, one from Emacs 22. In
Emacs 23, the underline is too close to the underlined characters.

Also, both the link characters and the underline seem too heavy in
Emacs 23.
 

In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
 of 2008-04-04 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/g/include
-fno-crossjumping'